Estimation of residual stresses in polymer-matrix composites using digital image correlation

In this study, the residual stresses in the laminated polymer-matrix composite sample with a configuration of [04/904]s were measured and investigated using the incremental hole-drilling and slitting methods combined with the digital image correlation (DIC) technique. By averaging the values of strain obtained by the DIC technique in the location of a virtual strain gauge, an equivalent strain was calculated. For this purpose, first, the feasibility of the average strain field data (using the averaging technique) was validated by the finite element (FE) analysis. The results show an acceptable accuracy of the equivalent strain obtained by averaging the strains obtained by the DIC technique in comparison with the value measured by the real strain gauge, for both the incremental hole-drilling and slitting methods. Furthermore, the corresponding residual stress values from incremental hole-drilling and slitting tests were compared with each other and also with theoretical residual stresses. According to the obtained results, the capability of the DIC technique in combination with the hole-drilling and slitting methods in calculating residual stresses was demonstrated.